@T2B - The image size of a digital photo is given by 2 attributes, its area in pixels, say 800 wide by 600 deep, and how many bits are used to represent each colour. For "true colour" this will be 24 bits per pixel. So the size of the example photo will be 800*600*24 = 11_520_000 bits. We normally express this in bytes: 1 byte is 8 bits, so this image is 1_440_000 bytes plus any metadata (data about the image, like what sort of camera and lens you used).
I can't see anything much more than that about the image except that it's already a jpeg, so it's about as compressed as it can get except by losing image size.